The use of steering columns which are collapsible in order to absorb impact energy during collisions are well known.
Many such steering columns employ a deformable member to absorb energy upon impact and the ensuing collapse of the steering column. For example, U.S. Pat. No. 4,627,306, issued to Berenjian, discloses a collapsible steering column which includes telescopically engaged upper and lower column tubes and a steering shaft rotatably disposed within the upper and lower column tubes. The upper column tube is mounted to a steering column support member, such as being affixed to the dashboard assembly with a bracket assembly. The bracket assembly includes a means for absorbing impact loads through plastic deformation as the upper and lower column tubes move together axially during a collision.
Energy dissipating materials have also been used. For example, U.S. Pat. No. 4,643,448, issued to Loren, discloses an energy absorption steering assembly which includes an elongated tubular adapter sleeve mounted to the underside of an instrument panel. An elongated steering column is slidably retained co-axially within the adapter sleeve. The adapter sleeve includes an annular radial sleeve flange extending inward from the side walls of the adapter sleeve to slidably engage the steering column. The steering column includes an annular radial column flange extending outwardly from the side walls of the steering column so as to slidably fit within the adapter sleeve. The cavity between the adapter sleeve and the steering column, defined at the ends by the annular radial sleeve flange and the radial column flange, is filled with an elastically deformable plastic foam. Accordingly, when axial impact loads are imposed upon the steering column, the plastic foam is elastically deformed, thereby absorbing some or all of the energy of the impact as the steering column is displaced axially relative to the adapter sleeve.